The artist used to produce the dustwrapper artwork is not identified, but was perhaps part of the Readers Union production department. There have been suggestions that the artwork was by Tolkien, but this is highly unlikely as there is no mention of this in the correspondence between Readers Union and Allen & Unwin.

What is the artwork supposed to represent?
The ring and eye are fairly obvious, and the upward spikes may be towers, but the rest is a bit of a mystery!